\documentclass{article}
% translate with >> pdflatex -shell-escape <file>

% This file is used as unit test for pgfplots, copyright by Christian Feuersaenger.
% 
% See
%   http://pgfplots.sourceforge.net/pgfplots.pdf
% for pgfplots.
%
% Any required input files (for <plot table> or <plot file> or the table package) can be downloaded
% at
% http://www.ctan.org/tex-archive/graphics/pgf/contrib/pgfplots/doc/latex/
% and
% http://www.ctan.org/tex-archive/graphics/pgf/contrib/pgfplots/doc/latex/plotdata/

\usepackage{pgfplots}
\pgfplotsset{compat=newest}

\pagestyle{empty}

\begin{document}
\begin{tikzpicture}[mark size=1.5pt,remember picture]

\begin{axis}[
  xmin=-5,xmax=5,
  %ymin=0,ymax=25,
  %ytick={0,5,...,25},
  xlabel={arc length distance $t$ from saddle [pixels]},
  ylabel={boundary indicator value $|\vec{b}_g(t)|$}]

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\addlegendentry{undesired, noise-induced edge}

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\addlegendentry{real, high-contrast image edge}

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\addlegendentry{real, low-contrast image edge}

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\addlegendentry{streamer (converging to real edges)}

\draw[dotted] (axis cs:0,0) -- (axis cs:0,14) node[right] {saddle pos};

\end{axis}

\end{tikzpicture}
\end{document}
